Comments

Great idea! Great minds think alike right?I was literally about to make an instructable for this... oh well you beat me too it! mine works fine for the pours as well... but it is a little rushed and kind of hard to control... but it works! Great going!

1) The molten material will leech impurities from the fire extinguisher metal as this metal will oxidize when heated to the temperatures needed. This is especially true if smelting aluminum alloys or pot metals for casting. These impurities lead to poor castings, bubbles, fissures, pocks, and other weaknesses within the cast.

2) The walls on this make-shift crucible are extremely thin. This will lead to faster heat dissipation, leading to uneven pours, and abnormalities within the cast.

3) This design has very little control. While pouring water, you have all the time in the world to steady yourself, and gain control over the pour. However, with the lack of insulating properties of the container, you will need to quickly go from the furnace to the pour, this leads to a " rushed " situation, which is often how accidents happen.

final note:

When talking about pouring molten metal, control, and safety are key concerns. This particular design, while may be used, is extremely unsafe. A proper crucible will have a rounded bottom on the inside for a complete pour out, will have an angled outside slope to allow it to be " grabbed " by tongs for greater pour control, and safety while moving from the furnace to the pour.

Add to all of this information, the fact that crucibles aren't very costly. You end up asking yourself a question:

This is a great idea! I've been looking all over for something steel that's the right shape for my soon-to-be-fired-up aluminum furnace, and never thought of an old fire extinguisher. Thanks for posting this!

P.S. Since you didn't end up covered in white dust when you did your first cut, I assume you discharged it first...you might want to mention that for, how should I say this, the most enthusiastic among us... ;-)